Mine goes about 4000-4500 miles between changes, on average. I tested my oil once using http://www.blackstone-labs.com/ to find out if the oil really could go 6000 miles between changes. The results indicated that yes, it could, but I am more cautious and don't want to push it that far. You will find a wide range of responses from different people. It's all about what you are comfortable with, as the Jeep is your machine.

There are a threads on this subject somewhere on here. It's dependent on where you drive and how you drive and how much. City vs hwy, are you towing or wheeling, are you using dinosaur oil or synthetic. When I was driving about 1000 miles a month I would change the oil every 4 months using full synthetic; now I drive about 750 miles a week, so I change it every 5-6K oil filter included. I don't tow or wheel too often either and conditions aren't too dusty.